Pazopanib Sensitivity in a Patient With Breast Cancer and FGFR1 Amplification.

Treatment options for patients with hormone receptor-positive (HR+), HER2-negative (HER2-) breast cancer and resistance to endocrine therapy remain limited. An interesting therapeutic target in these patients is fibroblast growth factor receptor 1 (FGFR1). FGFR1 is amplified in approximately 11% of patients with breast cancer, especially those with HR+ disease. This report presents a patient with metastatic HR+ HER2- breast cancer harboring an FGFR1 amplification who was resistant to endocrine therapy but responded to pazopanib, a multi-tyrosine kinase inhibitor with FGFR-inhibiting activity. Upon pazopanib treatment, the patient's brain lesions nearly disappeared, and she experienced therapeutic changes in the lung and an improvement of liver function. This case suggests that pazopanib may be a promising agent for the treatment of patients with breast cancer and FGFR1 amplifications.